Cut zucchini and summer squash in half lengthwise. Remove the insides of the bell peppers and cut into large chunks. Remove the top and bottom from the red onion and slice horizontally into three pieces.
Combine red wine vinegar, pepper, salt, oregano, and garlic.
Whisk in the olive oil and coat vegetables in the dressing. Place on a baking sheet.
Season the rib eye with salt and pepper.
Grill steak over medium-high heat for 5-7 minutes on each side (times may vary depending on the grill and how well-done you like your steak).
Add the vegetables to the grill and cook the zucchini and summer squash for 5-7 minutes on each side. Cook the bell peppers and onions 4-6 minutes each side (times may vary depending on the grill).
Remove steak from the grill and let rest for 10 minutes.
Slice the steak into strips.
Cut vegetables into small pieces. Arrange vegetables and steak on a bed of mixed greens.
Drizzle olive oil, red wine vinegar, salt, and pepper over the salad.