Pre-heat grill or grill pan to medium-high heat.
In a large bowl, toss chicken cubes with olive oil, salt, pepper, garlic powder, and oregano.
Place chicken bites on the grill surface or skewers.
Grill chicken for 3-4 minutes per side until the internal temperature reaches 165 degrees Fahrenheit.
In a separate bowl, whisk mayonnaise, minced garlic, lemon juice, and dijon mustard until smooth.
Remove chicken from heat and serve with the garlic sauce.