Given the well-documented relation between executive functioning (EF) and math skills in preschool, there is a surprising lack of evidence on early intervention approaches that have successfully, and consistently, impacted both EF and math skills. To confront this gap in the literature, Study 1 explored why an established EF intervention impacted children's math skills and not EF. Study II examined whether explicitly "combining" EF and math content may impact both children's math and EF skills. And finally, Study III examined the feasibility of combined math/EF content "in the classroom," and identified barriers to coaching, teacher implementation, and teacher understanding of the intervention components. More specifically, Study 1 performed a replication and extension analysis of the Tools of the Mind (Tools) program's lack of impact on children's EF skills but small impact on math skills (Head Start CARES study, Morris et al., 2014). This preschool classroom intervention-- which emphasizes planning, scaffolded play, and peer turn-taking--is theorized to improve children's EF skills, yet a meta-analysis of this curriculum has revealed more consistent impacts on math than EF skills, and two other studies found that higher fidelity of implementation at the end of this intervention was associated with "fewer" student EF gains. I approached this perplexing finding by taking a closer look at the fidelity of implementation of specific components of the intervention to determine if the documented low levels of fidelity in the Head Start CARES study was consistent across intervention components and time of year, and if subsequent variability in this more fine-grained measurement may be explaining the impacts on math and (lack thereof) on EF. Results illustrated that teachers who achieved high levels of fidelity on one component of the intervention (Play plans) within the first two months of implementation had students who made more gains in math. These teachers were also more likely to have a Bachelor's (BA) Degree. However, a subgroup analysis revealed that there was no impact of Tools on math when the sample was restricted to teachers with and without a BA degree, although teachers with a BA in the Tools group had children who made more (trending towards statistically significant) gains in math compared to children who had teachers with a BA in the control group ([beta] = 0.12, p = 0.09). This study implies that the documented impact of Tools on math skills is still not well-understood, although there is some evidence that high fidelity of implementation early on is contributing to the observed differences in children's math gains. Study II was more exploratory than Study I where I designed an explicitly combined math and EF preschool intervention. Although results from Study 1 indicated that interventions targeting EF skills may not be a promising approach for impacting math and EF skills, it is possible that there is a way to design the content of EF interventions to impact both EF and math simultaneously. In this study, I created a set of 12 activities that explicitly targeted children's math and EF skills. Pilot data revealed that 40 children who participated in a 7-week intervention where they played EF/math games with a researcher outside of the classroom made statistically significantly greater gains in EF skills (d=0.15)--but not math skills (d=0.07)--compared to children who were not taken out of the classroom to play these games. In Study III, I brought activities from Study II into the classroom setting to identify the strengths and weaknesses of the content and coaching of the intervention from the perspective of preschool teachers and coaches. I trained ten Head Start preschool teachers and four instructional coaches on the implementation of these activities during large- and small-group settings. Although I collected no child-level measures, I used these feasibility data in preparation for a randomized-controlled trial (that is beyond the scope and funding of this dissertation). Observational data revealed that after 16 weeks of modeling, implementation, and feedback, teachers were able to implement these activities in the classroom with adequate fidelity, and children were rated as exhibiting mid to high levels of engagement on 10 out of 12 activities. When observed, teachers struggled the most with achieving fidelity in following the math skill sequence of each of the activities, despite implementing the EF integration with ease. However, when teachers were tested on their understanding of math skill sequence and EF integration for each of the activities, teachers struggled the most with identifying how children's EF skills were actually exercised within each activity. This has implications for how we educate teachers on the components of an intervention. Teachers' fidelity of implementation may also not reflect what they actually understand about the intervention. Qualitative data further highlighted strengths of the intervention and coaching where teachers lauded the in-classroom modeling of activities, breakdown of math skill levels for each activity, and variety of math topics covered. Noteworthy suggestions from teachers and coaches for future iterations of these math and EF activities included more coaching on how to help children with the most basic math skill level, aligning activities with the Desired Results Developmental Profile (DRDP) assessment and teachers' lesson plans, and aligning coaching with Classroom Assessment Scoring System (CLASS) goals. Overall, this dissertation highlights the complexity of how early interventions impact EF and math skills and discusses the implications for research and practice. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]