Lemon juice and fresh mint add bright notes to a quick saute, which would make an ideal accompaniment to grilled chicken or fish.
Heat half the olive oil in a large skillet over medium-low heat. Cook garlic and onion, stirring, until translucent but not yet softened, about 2 minutes.
Increase heat to medium-high. Add the remaining oil along with the zucchini, squash, and crushed red pepper. Cook, stirring occasionally, until vegetables are tender and golden brown, about 5 minutes. Remove from heat, stir in the lemon juice, and season with salt and pepper. Transfer to a serving dish, sprinkle the mint on top, and serve immediately.
When cooking this dish, do not crowd the vegetables, or they will steam instead of browning. If your skillet is not large enough, cook them in two batches.