Pat the chicken breast cubes dry and season with salt and black pepper.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat.
Add the chicken to the skillet in a single layer and sear until golden brown and cooked through, approximately 6 to 8 minutes; remove chicken and set aside.
Add the remaining 1 tablespoon of olive oil to the same skillet.
Add the sliced zucchini and yellow squash to the skillet and sauté for 4 to 5 minutes until tender-crisp.
Stir in the minced garlic, dried oregano, and red pepper flakes, cooking for an additional 1 minute until fragrant.
Return the cooked chicken to the skillet and toss to combine all ingredients.
Remove from heat, drizzle with lemon juice, and serve immediately.